Medical device for selective intrathecal spinal cooling in aortic surgery and spinal trauma

ABSTRACT

The invention provides a medical device having two elongate catheters, a pump, a refrigeration system, and a manometer. Each catheter has a proximal end, a distal end, a lumen therebetween and communicating with a distal port. The proximal ends of the catheters are connected to the pump and the refrigeration system. The distal ends are adapted for insertion into the subarachnoid space. The cerebral spinal fluid is aspirated from the first catheter to the pump, cooled to below body temperature, and returned to the second catheter. The flow rate of the cerebral spinal fluid is adjusted according the CSF pressure and temperature. Methods of using the devices in treating patients suffering from spinal trauma and undergoing aortic surgery are also disclosed.

[0001] This is a continuation of U.S. application Ser. No. 09/287,969,filed Apr. 7, 1999, which is a continuation-in-part of U.S. applicationSer. No. 09/260,370, filed Mar. 1, 1999, now abandoned, the contents ofeach are expressly incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

[0002] The present invention generally relates to medical devices usefulin reducing and preventing spinal injury in patients with spinal traumaor patients undergoing aortic surgery. More specifically, the inventionprovides devices for insertion into the subarachnoid space forcirculating and cooling the cerebral spinal fluid below bodytemperature. The flow rate of the cerebral spinal fluid is variablyadjusted according to the pressure and temperature, respectivelymeasured by a manometer and thermometer.

BACKGROUND OF THE INVENTION

[0003] Spinal ischemia resulting in neurological complications occurs inpatients sustaining a traumatic injury to the spinal cord or patientsundergoing aortic surgery. Spinal cord injury can be classified aspenetrating or blunt. In penetrating injuries, such as stab wound or gunshot wound to the spinal cord, complete severing of the spinal cord canoccur, resulting in total muscular paralysis and loss of sensation belowthe level of injury. This condition of flaccid paralysis and suppressionof all reflex activity following immediately upon transection of thespinal cord and involving all segments below the lesion is referred toas spinal shock. In most cases, reflex activity returns within 1 to 6weeks from the onset of the spinal shock. Once transection of the spinalcord has occurred, peripheral reinnervation by the nervous system doesnot occur.

[0004] Spinal shock also occurs in blunt injuries, such as in motorvehicle accident, where compression of the spinal cord by impingementfrom fractured or dislocated vertebral bodies results in sensory andmotor impairment below the level of cord involvement. Diagnosis ofspinal fracture or dislocation is often made on X-rays. Spinal cordcompression can be diagnosed on MRI, CT scan with myelogram, or lumbarpuncture (Queckenstedt test). The mechanism of spinal ischemia is mostlycaused by swelling of the cord. In these patients, hypotension may alsooccur as a result of loss of vascular sympathetic tone in the involvedarea. Urinary and/or bowel incontinence is a common complication due toimpaired autonomic function.

[0005] Spinal ischemia is also a common postoperative complicationfollowing aortic surgeries, such as abdominal aortic aneurysmectomy. Theincidence of spinal cord ischemia/stroke during aortic surgery istypically over 10%. During abdominal aortic aneurysm (AAA) repair, forexample, the spinal arteries, which provide blood supply to the spinalcord, are often severed from the diseased aorta, and some but not all ofwhich are later resutured to the prosthetic graft. As a result, bloodflow to the spinal cord is reduced. When reduction of spinal perfusionlasts the duration of the surgery, typically more than forty-fiveminutes, spinal ischemia/stroke may ensue, often resulting in anteriorspinal artery syndrome. The classic syndrome is characterized byparaplegia, rectal and urinary incontinence, loss of pain andtemperature sensation, but with sparing of vibration and proprioceptivesense. Patients may also sustain neurologic deficits in the lowerextremities after abdominal aortic surgery due to loss of posteriorcolumn modalities.

[0006] Brain damage associated with either stroke or head trauma isworsened by hyperthermia and improved with hypothermia. Currenttreatment for acute ischemic stroke and head injury is mainlysupportive. A thrombolytic agent, e.g., tissue plasminogen activator(t-PA), can be administered to stroke patients who have nocontraindication to t-PA. Current treatment for patients suffering fromspinal injury is also supportive, e.g., to secure local hemostasis andto prevent infection by appropriate debridement, closure, andadministration of antibiotics in penetrating spinal injury. In patientssuffering from blunt injuries, surgical decompression of the spinal cordmay be performed to restore neurological function. Spinalischemia/stroke due to aortic surgery is also treated with supportivetherapy, e.g., maintaining hemodynamic stability and monitoringneurological status, while waiting for the neurological deficits torecover with time. Therefore, besides surgical intervention in bluntinjury, there is currently no good treatment which reduces neurologicdamage to the spinal cord.

[0007] New devices and methods are thus needed in treating spinalischemia/stroke in patients having spinal cord trauma or aortic surgery,in preventing spinal ischemia in patients anticipating a majorthoracoabdominal surgery, or in cerebral ischemia, which minimizesneurological complication and improves the patients' quality of lifewithout causing significant side effects.

SUMMARY OF THE INVENTION

[0008] The invention provides devices and methods for reducingneurologic complications in patients sustaining trauma to the spinalcord or undergoing aortic surgery. More specifically, the inventionprovides devices and methods for cooling the cerebral spinal fluid (CSF)surrounding the spinal cord.

[0009] A first embodiment of the device comprises two elongatecatheters, each having a proximal end, a distal end, and a lumencommunicating with a port at the distal end. The distal ends of thefirst catheter and the second catheter are adapted for insertion into apatient's subarachnoid space. The proximal ends of the catheters areconnected to a pump to facilitate circulation of the CSF through thelumens of the catheters. A refrigeration system is connected to the pumpto provide adjustable cooling of the CSF, such that CSF flowing throughthe lumen of the first catheter is cooled to below body temperaturebefore flowing into the lumen of the second catheter. The CSF pressurein the circuit is measured by a manometer included in the catheters, thepump, or the refrigeration system. It will be understood that althoughthe pump is advantageous, it may not be included in all embodiments forcirculation of the CSF.

[0010] In another embodiment, the distal end of each catheter carries aneedle which facilitates introduction of the devices into thesubarachnoid space. A suture flange is mounted on a distal region of thefirst catheter and/or the second catheter for securing the devices afterinsertion into the subarachnoid space. Other embodiments of the devicesinclude radiopaque markers mounted at the distal end of each catheterfor identifying the position of the catheters in the subarachnoid space.

[0011] In still another embodiment, the proximal end of each catheterincludes a port for infusing fluid, such as Ringer's lactate solution,or pharmaceutical agents into the subarachnoid space. The port can beused to drain the CSF for reducing pressure in the subarachnoid space.Alternatively, a release valve may be included proximally in one of thecatheters to drain the CSF when the pressure exceeds a desiredthreshold. A distal region of each catheter may be angled relative tothe proximal end to facilitate entry and rostral advancement in thesubarachnoid space.

[0012] In still another embodiment, the devices include at least onethermometer. The thermometer can be included in the proximal end of thefirst and/or second catheter for measuring the temperature of the CSF orCSF/fluid mixture entering and exiting the subarachnoid space.

[0013] The methods for cooling the spinal cord to prevent neurologicdamage during inadequate spinal perfusion utilize the devices disclosedherein. In a first method, the distal end of the first catheter isinserted percutaneously between the spinous processes of lumbarvertebrae L3 and L4 or L4 and L5 into the subarachnoid space. The distalend of the second catheter is inserted in the lumbar region at a levelabove or below the insertion of the first catheter. The second catheteris advanced rostrally in the subarachnoid space so that the distal portis positioned preferably in the low cervical or high thoracic region ofthe spine or optionally in the lumbar region. The position of thecatheters can be verified under fluoroscopy in the embodiments where thedistal ends of the catheters include one or more radiopaque marker.Preferably, the CSF is aspirated from the first catheter, cooled by therefrigeration system, and passed into the second catheter.Alternatively, the CSF is aspirated from the second catheter, cooled bythe refrigeration system, and passed into the first catheter. In thismanner, the CSF is cooled to below normal body temperature, which can bemonitored by thermometers included in either or both catheters. Thegreater the cooling the greater the degree of protection is likely forthe spinal cord.

[0014] In another method, after insertion of the catheters, the CSF isdrained in the lumbar region to reduce the CSF pressure to zero. The CSFpressure can be monitored by a manometer included in either or bothcatheters. The CSF is collected in a bag and discarded after theprocedure. Fluid, such as Ringer's lactate, is infused through one ofthe catheters, preferably the second catheter, and drained passivelythrough the first catheter. The CSF collected in a bag may be discardedor reintroduced at the end of the procedure. The CSF/Ringer's lactatemixture is cooled through the refrigeration system and circulated byactivating the pump. The pump can be either volume limited or pressurelimited. The temperature of the CSF mixture can be reduced rapidly, andthe flow rate is adjusted to maintain the desired temperature. The CSFpressure is maintained preferably at a minimum, i.e., at approximatelyzero, to maximize perfusion to the spinal cord.

[0015] In still another embodiment, a port protecting mechanism, e.g., anet or a fence guard, is mounted at the distal ends of the catheters.When the pump is activated, the mechanism prevents the arachnoid fromfolding over and obstructing the suction and port, and prevents nerveroots from being sucked into the catheter. The mechanism may be anintegral part of the catheter, or be operably mounted on the innercatheter wall and deployed when the needle is withdrawn.

[0016] In still another method, the distal end of the first catheter isinserted between the spinous processes of lumbar vertebrae L3 and L4 orL4 and L5 into the subarachnoid space. The distal end of the secondcatheter is inserted between the spinous processes of low cervicalvertebrae or high thoracic vertebrae, e.g., between C-6 and C-7, betweenC-7 and T-1, or between T-1 and T-2, into the subarachnoid space. TheCSF is aspirated preferably through the first catheter, cooled throughthe refrigeration system to below body temperature, and passed into thesecond catheter. Alternatively, the CSF is aspirated from the secondcatheter in the low cervical or high thoracic region and passed into thefirst catheter in the lumbar region to provide spinal cooling. Thismethod may be desirable in situations where the second catheter can notbe advanced rostrally in the subarachnoid space due to an edematousspinal cord after injury.

[0017] It will be understood that although the devices and methods aremost useful in treating patients with spinal trauma or undergoing aorticsurgery, they can be utilized to reduce neurologic damage duringcerebral hypoperfusion in situations, such as cardiac arrest, cardiacfailure, low cardiac output states, stroke, head injury, cerebralaneurysm surgery, open and closed cardiac surgery and aortic surgery.Selective cooling of the cerebral tissues is preferred over systemiccooling, which may have undesirable effects on the heart and otherorgans and induce systemic coagulopathy. In using the devices, thedistal end of the first catheter is inserted between the low cervicalvertebrae or high thoracic vertebrae into the subarachnoid space. Thedistal end of the second catheter is inserted either in the lumbarregion as described above or between the cervical vertebrae, in theforamen magnum, or through a skull burr hole into the subarachnoid spaceor the lateral ventricle. The CSF is preferably aspirated from the firstcatheter in the cervical subarachnoid space, cooled to below bodytemperature, and passed through the second catheter into thesubarachnoid space in the cervical region or the brain. The patients maybe tilted back and forth to improve circulation of the hypothermic CSFin patients with stroke, head trauma, or spinal injury. The flow rate ofthe CSF is adjusted according to the CSF temperature and pressure tomaximize hypothermic protection on the cerebral tissues.

[0018] It will be understood that there are several advantages in usingthe devices and methods disclosed herein for reducing neurologicalcomplications which occur during aortic surgery or trauma. For example,the devices can be used (1) to provide continuous and variable spinalcooling, (2) in patients with either blunt or penetrating spinal traumaimmediately after injury, (3) to selectively provide protectivehypothermia to the spinal cord, thereby avoiding complicationsassociated with systemic cooling, (4) by an anesthesiologist prior toaortic surgery, (5) to reduce neurologic deficits during cerebralhypoperfasion in patients with, e.g., stroke, cardiac failure, orcardiac surgery, (6) during aortic surgery, such as AAA repair, tolengthen the window for reattachment of the spinal arteries, and (7) toprovide intrathecal administration of neuroprotective agents.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 depicts blood supply and venous drainage of the spinalcord.

[0020]FIG. 2 depicts the relation of spinal cord segments to an adultpatient's vertebral column.

[0021]FIG. 3 depicts an embodiment of the medical device for providingspinal cord cooling according to the present invention.

[0022]FIG. 4 depicts another embodiment of the medical device forproviding spinal cord cooling according to the present invention.

[0023]FIG. 5A depicts a distal end of another embodiment of the deviceincluding a needle.

[0024]FIG. 5B depicts the distal end of the needle of FIG. 5A enteringthe subarachnoid space.

[0025]FIG. 5C depicts the distal end of the device of FIG. 5A enteringthe subarachnoid space.

[0026]FIG. 6A depicts another embodiment of the needle carried at thedistal end of a catheter.

[0027]FIG. 6B depicts the needle of FIG. 6A inserted in the subarachnoidspace.

[0028]FIG. 6C depicts the needle and the distal end of the catheter ofFIG. 6A inserted in the subarachnoid space.

[0029]FIG. 6D depicts the needle of FIG. 6A being removed from thecatheter.

[0030]FIG. 6E depicts the device of FIG. 6A inserted in the subarachnoidspace without the needle.

[0031]FIG. 7 depicts the catheters of the device of FIG. 4 inserted inthe lumbar region.

[0032]FIG. 8 depicts the catheters of another embodiment of the deviceinserted in the lumbar and cervical region.

[0033]FIG. 9 depicts the device according to the present inventioninserted in various cranial locations to provide cooling to the cerebraltissue.

[0034]FIG. 10A depicts another embodiment of the catheter having adistal bendable region which assumes a linear configuration relative tothe proximal end of the catheter.

[0035]FIG. 10B depicts the catheter of FIG. 10A having the distalbendable region assuming an angled configuration relative to theproximal end of the catheter.

[0036]FIG. 11A depicts another embodiment of the catheter having adistal bendable region and a side port.

[0037]FIG. 11B depicts the catheter of FIG. 11A inserted in thesubarachnoid space.

[0038]FIG. 11C depicts a distal region of the catheter of FIG. 11Bassuming an angled configuration relative to the proximal end of thecatheter.

[0039]FIG. 12A depicts one embodiment of a port protecting mechanismhaving a net mounted over the distal port of the catheter.

[0040]FIG. 12B depicts another embodiment of the port protectingmechanism having a fence guard mounted over the distal port of thecatheter.

[0041]FIG. 12C depicts one embodiment of the port protecting mechanismmounted in the inner wall of the catheter.

[0042]FIG. 12D depicts the port protecting mechanism of FIG. 12C afterbeing activated by withdrawing the needle.

[0043]FIG. 12E depicts another embodiment of the port protectingmechanism having a moveable hinge mounted in the inner wall of thecatheter.

[0044]FIG. 12F depicts the port protecting mechanism of FIG. 12Ecovering the distal port of the catheter.

DETAILED DESCRIPTION

[0045] The spinal cord, part of the central nervous system, is locatedin the vertebral canal (neural canal) which contains the spinal cord,its protective membranes, called spinal meninges, and associated vesselsembedded in loose connective and fatty tissue. The spinal meningesinclude pia mater 5, arachnoid mater 6, and dura mater 7 as depicted inFIG. 1. The subarachnoid space is formed between the pia mater andarachnoid mater. The epidural (extradural) space is formed between thearachnoid mater and the dura mater. During lumbar puncture, for example,the spinal needle is inserted into the lumbar interspinous space, andpenetrates the dura mater and arachnoid mater to reach the subarachnoidspace.

[0046] The spinal cord is supplied by three longitudinal arteries, i.e.,an anterior spinal artery and two posterior spinal arteries, which arereinforced by segmental vessels called radicular arteries. These vesselsare derived from branches of the vertebral, deep cervical, intercostal,and lumbar arteries, all of which branch from the aorta. In FIG. 1,anterior spinal artery 1, formed by two small branches from thevertebral arteries, supplies the anterior two-third of the spinal cord.Posterior spinal arteries 2, arise as small branches of either thevertebral or the posterior inferior cerebellar arteries, supply theposterior one-third of the spinal cord. Fracture and/or dislocations ofthe spinal column may interfere with blood supply to the spinal cordfrom the spinal arteries. The blood supply by the anterior and posteriorspinal arteries is sufficient only for the superior cervical segments ofthe spinal cord. The remaining segments receive most of their bloodsupply from the radicular arteries, which supply the vertebrae,meninges, and the spinal arteries. Great anterior radicular artery 3(also known as artery of Adamkiewicz) arises from an inferiorintercostal or a superior lumbar artery. This artery is clinicallyimportant because it contributes to the anterior spinal artery, andtherefore, when the intercostal or lumbar artery is severed, e.g.,during aortic surgeries, the main blood supply to the inferior two-thirdof the spinal cord is compromised. These patients may lose all sensationand voluntary movement distal to the level of impaired blood supply tothe spinal cord.

[0047] The relation of spinal cord segments 20 to the adult vertebralcolumn is illustrated in FIG. 2. The spinal cord lies in the spinalcanal surrounded by vertebral bodies 22 anteriorly and spinous processes23 posteriorly. The spinal cord begins as a continuation of the inferiorpart of the brain stem. In adults the spinal cord usually ends oppositethe intervertebral disc between L1 and L2 vertebrae. There are 31 pairsof spinal nerves attached to the spinal cord by dorsal and ventral roots21. The bundle of nerve roots in the subarachnoid space caudal to thetermination of the spinal cord is cauda equina 25. The cerebral spinalfluid is usually obtained from the lumbar subarachnoid space between thespinous processes of L3 and L4 or L4 and L5 vertebrae because the spinalcord ends above these levels and is not likely to be damaged by a lumbarpuncture needle or catheter.

[0048]FIG. 3 depicts a first embodiment of the device for cooling thespinal cord to prevent neurologic damage during inadequate spinalperfusion. The device includes two elongate catheters. First catheter 30has lumen 33, proximal end 31, and distal end 32. The lumen communicateswith port 35 at the distal end. Second catheter 40 has lumen 43,proximal end 41, and distal end 42. Lumen 43 communicates with port 45at the distal end. Distal ends 32 and 42 are adapted for attachment to alumbar puncture needle. Pump 50 is connected to proximal end 31 and 41of the respective first and second catheters. Cooling system 52 isconnected to pump 50 to provide variable cooling of the CSF. Proximalend 31 of the first catheter also includes manometer 55 for measuringCSF pressure in the circuit.

[0049]FIG. 4 depicts another embodiment of the spinal cooling device.The device includes first and second catheter 30 and 40, each having,respectively, proximal end 31 and 41, distal end 32 and 42, and lumen 33and 43. The proximal ends of the catheters are connected to pump andcooling unit 51, capable of providing circulation and cooling of the CSFin the circuit. The proximal end of the first catheter also includesmanometer 55 and thermometer 60 for measuring, respectively, CSFpressure and temperature exiting or entering the first catheter. Theproximal end of the second catheter also includes second thermometer 61for measuring CSF temperature exiting or entering the second catheter.When the CSF pressure exceeds a desired threshold, the CSF can bedrained from release valve 65 included in the first catheter or port 64included in the second catheter. Port 64 can also be used to administerfluid or pharmaceutical agents into the subarachnoid space. Each distalend of the catheters carries needle 66, which facilitates introductionof the catheter into the subarachnoid space.

[0050]FIGS. 5A, 5B, and 5C depict distal ends of an embodiment of thedevice carrying a needle. In FIG. 5A, needle 66 is carried in lumen 33of distal end 32 of the catheter. Distal end 67 of the needle protrudesdistally from port 35. The needle is movable within the lumen of thecatheter by operating mechanism 68, capable of reversibly locking andreleasing the needle in the lumen.

[0051] In use, distal end 67 of the needle is inserted through softtissue 71 between the spinous processes of two vertebrae intosubarachnoid space 70 as depicted in FIG. 5B. Once the entry of thesubarachnoid space is confirmed by the back-flow of the CSF through theneedle into lumen 33, mechanism 68 is operated to release the needle inthe lumen. Distal end 32 of the catheter is advanced distally over theneedle to insert in the subarachnoid space as depicted in FIG. 5C. TheCSF is then circulated through port 35 and lumen 33 of the catheter.

[0052] Another embodiment of the catheter carrying a needle at itsdistal end is depicted in FIGS. 6A, 6B, 6C, 6D, and 6E. In FIG. 6A,distal end 32 of the catheter includes second lumen 34 for housingneedle 66. Lumen 34 communicates with lumen 33 of the catheter, distallywith port 35, and proximally with port 36. Needle 66, which has distalend 67 and proximal end 68, is slidably movable in lumen 34. Distal end67 protrudes distally from port 35, and proximal end 68 protrudesproximally from port 36. Suture flange 69 is slidably mounted on distalend 32 of the catheter.

[0053] In use, distal end 67 of the needle is inserted through softtissue 71 between spinous processes of two vertebrae into subarachnoidspace 70 as depicted in FIG. 6B. While holding proximal end 68 of theneedle, the distal end of the catheter is advanced distally over theneedle to insert in the subarachnoid space as depicted in FIG. 6C.Needle 66 is removed from subarachnoid space 70 by pulling on end 68proximally as depicted in FIG. 6D. Sutures can be placed between sutureflange 69 and soft tissue 71 to secure the catheter. The needle canremain in lumen 34 or be removed completely from lumen 34. In FIG. 6E,after removal of the needle, the CSF is circulated through port 35 andlumen 33. Port 36 can also be used as a release valve for draining theCSF when the CSF pressure exceeds a desired threshold or as an infusionport for administering fluid, such as Ringer's lactate solution, orpharmaceutical agents into the subarachnoid space.

[0054] The devices disclosed herein are useful in reducing neurologicinjury to the spinal cord following spinal trauma or aortic surgery byproviding cooling of the CSF surrounding the spinal cord. In FIG. 7, thedevice of FIG. 4 is shown inserted in a patient's lumbar region. Understerile condition, two lumbar punctures are performed. Needle 66,preferably 14 Gauge, carried in distal end 32 of first catheter 30 isinserted between spinous processes 23 of L4 and L5 into subarachnoidspace 70. Needle 66 carried in distal end 42 of second catheter 40 isinserted between the spinous processes of L3 and L4 into subarachnoidspace 70. In alternative methods, the needle and catheter may beinserted between L5 and S1, L2 and L3, or L1 and L2. The catheters areadvanced distally over the needle so that port 35 and 45 receive theCSF. Port 35 of the first catheter is positioned in the lumbarsubarachnoid space, whereas distal end 42 of the second catheter isadvanced rostrally in the subarachnoid space until it is positioned inthe low cervical or high thoracic region. Port 45 is shown positionedbetween the spinous processes of C7 and T1. Radiopaque markers may bemounted on the distal ends of the catheters so that the position of thedistal ends can be confirmed radiologically. Insertion of the twocatheters in the lumbar region is preferred because spinal cord 75usually terminates about L2, and damage to the spinal cord due toinstrumentation is not likely. Prior to the aortic surgeries, such asabdominal aneurysm repair, the device may be inserted by ananesthesiologist, so that the surgeon would not be inconvenienced.

[0055] After the catheters are secured in the subarachnoid space, theCSF from the lumbar region may be drained through release valve 65 toreduce the CSF pressure to approximately zero, which is measured bysecond manometer 56, optionally included in the distal end of thecatheter. The CSF is normally collected in a bag and may be discarded orreintroduced after the procedure. Large bore catheters, e.g., 3 or 4French, may be used to rapidly drain the CSF (at approximately 100-150cc in 3-4 minutes), thereby eliminating the need of using suction, whichmay cause the arachnoid to obstruct the distal ports or inadvertentdamage by suction on a nerve root. Fluid, such as Ringer's lactate, isinfused through the second catheter and drained passively through thefirst catheter. Preferably, this CSF and Ringer's lactate mixture iswithdrawn from the first catheter in the lumbar region, cooled by pumpand cooling unit 51, and passed into the second catheter in the lowcervical/high thoracic region. Alternatively, the CSF is withdrawn fromthe second catheter and passed into the first catheter. Any cooling ofthe CSF is beneficial in protecting the spinal cord from ischemicinjury. The greater the cooling, the greater the degree of protection.The temperature of the CSF exiting and entering the subarachnoid spacein the lumbar region is measured by thermometers 60 and 61,respectively. Using this method, the CSF temperature can be reducedrapidly. The flow rate of the recirculated CSF mixture can be adjustedto keep the CSF temperature and pressure at a desired level. It isdesirable to keep the CSF pressure at a minimum, at approximately zero,to maximize any remaining perfusion in the spinal cord after injury. Thecooling of the spinal cord and/or can be maintained during and/orseveral hours after aortic surgery, and be maintained several hoursfollowing spinal cord trauma or stroke. At the end of the coolingperiod, the CSF temperature is allowed to rise slowly. The catheters arethen removed from the lumbar region.

[0056] Instead of having the second catheter inserted in the lumbarregion, the second catheter can be inserted in the low cervical or highthoracic region. In FIG. 8, distal end 32 of first catheter 30 isinserted in the lumbar subarachnoid space between L4 and L5, whereasdistal end 42 of second catheter 40 is inserted in the cervicalsubarachnoid space between C6 and C7. The distal ends of the cathetersmay be advanced over a needle into the subarachnoid space as describedin FIGS. 5A, 5B, and 5C. This method may be preferred in situationswhere spinal cord 75 is very swollen and rostral advancement of thesecond catheter through the lumbar region is difficult. The secondcatheter may be inserted in the cervical region by a radiologist underfluoroscopy.

[0057] After the catheters are secured in the subarachnoid space, theCSF is aspirated through either catheter to the pump, cooled to belowbody temperature through a refrigeration system, and passed to the othercatheter. Preferably, the CSF is aspirated from the first catheter inthe lumbar region, and the cooled CSF or CSF/Ringer's lactate mixture isreturned to the second catheter in the cervical region, closer to thesite of spinal injury.

[0058] Circulation of hypothermic CSF by inserting the distal ends ofthe first and second catheters in the spinal region may be sufficient toprotect the brain in patients suffering from focal or hemisphericalischemia, since the spinal CSF communicates with the cerebral CSF.Alternatively, cooling of the cerebral CSF can be achieved by insertingthe distal end of the first catheter between the spinous processes oftwo cervical vertebrae, and inserting the distal end of the secondcatheter in the cervical region 90 into spinal subarachnoid space 91,through foramen magnum 92 into cerebellomedullary cistern 93, or throughskull burr hole 94 into the subarachnoid space 95 as depicted in FIG. 9.Alternatively, the second catheter can be inserted through a burr holeinto the lateral ventricle (not shown). The CSF is preferably aspiratedfrom the first catheter in the cervical region, cooled to below bodytemperature, and returned to the second catheter. The patient may begently tilted back and forth to improve circulation of the CSF. Thismethod is useful in situations where neurologic complications arise as aresult of inadequate cerebral perfusion, such as cardiac arrest, cardiacfailure, low cardiac output states, stroke, head injury, cerebralaneurysm surgery, open and closed cardiac surgery and aortic surgery.Selective cerebral cooling is advantageous over systemic cooling in thatcomplications due to systemic cooling, such as cardiac arrhythmia,disseminated intravascular coagulopathy, and poor healing, can beavoided.

[0059] It will be understood that cooling of the brain and the spinalcord by intrathecal circulation of hypothermic CSF or CSF/Ringer'slactate mixture can be achieved by inserting the first catheter in thelumbar region and the second catheter in any spinal level or throughskull burr hole in the ventricle. For example, intrathecal cooling ofthe cerebral tissue can be achieved by inserting the first catheter inthe lumbar region and the second catheter one level immediately above orbelow the level of the first catheter insertion.

[0060]FIGS. 10A and 10B depict another embodiment of the catheter havingbendable region 80 at distal region 32. In FIG. 10A, the distal end ofthe catheter is inserted through soft tissue 71 into subarachnoid space70. As needle 66 is inserted through bendable region 80 and protrudesdistal to port 35 into the subarachnoid space, distal region 32 assumesa linear configuration relative to the proximal end of the catheter.Once the entry of subarachnoid space 70 is confirmed by the back-flow ofthe CSF through needle 66 into lumen 33, mechanism 68 is operated torelease the needle in the lumen. Distal region 32 of the catheter isadvanced distally over the needle to insert in the subarachnoid space asdepicted in FIG. 10B. As bendable region 80 is advanced distally in thesubarachnoid space over needle 66, distal region 32 assumes an angledconfiguration relative to the proximal end of the catheter. Distal port35 can be positioned rostrally as shown in FIG. 10B or positionedcaudally.

[0061]FIGS. 11A, 11B, and 11C depict another embodiment of the devicefor intrathecal cooling of the CSF having bendable region 80 and sideport 82 at distal region 32 of the catheter. In FIG. 11A the catheterhas first lumen 33 and second lumen 84. The first lumen communicateswith distal port 35, needle lumen 34, and proximal end 31, whichincludes thermometer 60 for measuring CSF temperature. The needle lumencommunicates proximally with port 36, which can be used to drain CSFwhen the CSF pressure exceeds a desired threshold, or as an infusionport for administering fluid, such as Ringer's lactate solution, orpharmaceutical agents into the subarachnoid space. The second lumencommunicates with side port 82 and proximal end 85, which includesmanometer 55 for measuring CSF pressure. Cooling system 52 is connectedto proximal ends 31 and 85 to provide variable cooling of the CSF.Slidable suture flange 69 is mounted on the catheter proximal to sideport 82. Lumens 33 and 84 may be joined distally and separatedproximally. Distal region 32 assumes a linear configuration relative toa proximal end of needle lumen 34.

[0062] In use, needle 66, which protrudes distal to port 35, is insertedin the subarachnoid space. Distal region 32 of the catheter, in a linearconfiguration with the proximal end of lumen 34, is advanced over theneedle to insert in subarachnoid space 70 as shown in FIG. 11B. Asbendable region 80 and side port 82 are advanced distally to position insubarachnoid space 70 as depicted in FIG. 11C, distal region 32 assumesan angled configuration relative to the proximal end of lumen 34 anddistal port 35 is positioned rostrally in the subarachnoid space.Position of side port 82 is verified by back-flow of the CSF in lumen84. The needle may be removed from lumen 34, leaving port 36 availableto drain the CSF or infuse Ringer's lactate solution. Sutures can beplaced on suture flange 69 to secure the catheter onto soft tissue 71.Preferably, the CSF is drained by gravity or by a pump from port 82,passed through lumen 84, cooled by the cooling system, and returned toport 35 through lumen 33 and 34. In this way, circulation of hypothermicCSF for protecting the brain and the spinal cord is achieved byinserting the device through a single spinal level, thereby eliminatingthe need for two spinal punctures.

[0063] The distal end of the catheter may include a port protectingmechanism to protect the arachnoid from folding over or a nerve rootfrom being sucked into the distal port of the catheter, especially whenthe pump is used. In FIG. 12A, net 86, which is mounted over port 35 atthe distal end of the catheter, allows needle 66 to protrude distal toport 35 and prevents soft tissue from entering the port. In FIG. 12B,fence guard 87, another embodiment of the port protecting mechanism, ismounted at the distal end of the catheter. Needle 66 is inserted throughthe center of the fence guard. Both the fence guard and the needleprotrude distal to port 35. In FIG. 12C, releasable protecting mechanism88, operably associated with needle 66, is mounted in the inner wall ofthe distal end of the catheter. As needle 66 is withdrawn from distalport 35 as shown in FIG. 12D, protecting mechanism 88 is releaseddistally overlying port 35, thereby preventing the arachnoid or a nerveroot from entering the port during suction. In FIG. 12E, net 90, havinga dome-like frame, is mounted on the distal end of the catheter by hinge89. The hinge allows net 90 to open and close, thereby covering thedistal port of the catheter. When net 90 is positioned adjacent theinner wall of the catheter, needle 66 is advanced distal to the opendistal port, as depicted in FIG. 12E, for insertion of the catheter intothe subarachnoid space. After needle 66 is withdrawn from the distalport, net 90 operates about hinge 89 to cover the distal port, asdepicted in FIG. 12F, allowing the CSF, and not the arachnoid or nerveroot, to enter the lumen of the catheter.

[0064] The length of the catheter will generally be between 20 to 100centimeters, preferably approximately between 30 and 60 centimeters. Theinner diameter of the catheter will generally be between 0.1 and 0.6centimeters, preferably approximately 0.3 centimeters. The foregoingranges are set forth solely for the purpose of illustrating typicaldevice dimensions. The actual dimensions of a device constructedaccording to the principles of the present invention may obviously varyoutside of the listed ranges without departing from those basicprinciples.

[0065] Although the foregoing invention has, for the purposes of clarityand understanding, been described in some detail by way of illustrationand example, it will be obvious that certain changes and modificationsmay be practiced which will still fall within the scope of the appendedclaims.

What is claimed is:
 1. A method for preventing neurologic damage,comprising the steps of: providing first and second elongate tubularmembers, each member having a lumen communicating with a port at adistal end; inserting the first tubular member between lumbar vertebraeinto the subarachnoid space; inserting the second tubular member betweenlumbar vertebrae into the subarachnoid space, and advancing the distalport cephalad and locating the port in the cervical or thoracic regionof the spine; aspirating or draining cerebral spinal fluid (CSF) fromthe spinal column through one of the first tubular member or secondtubular member; cooling the CSF by extracorporeal refrigeration; andperfusing the CSF into the spinal column through the other of the firsttubular member or second tubular member, wherein the spinal cord iscooled to below normal body temperature, and wherein CSF pressure isreduced to and maintained at a level substantially below normal CSFpressure.
 2. The method of claim 1 , wherein the first and secondtubular members are inserted over a needle.
 3. The method of claim 1 ,further comprising the step of measuring CSF pressure using a manometer.4. The method of claim 1 , wherein the method cools the spinal cord toprevent neurologic damage during inadequate spinal perfusion.
 5. Themethod of claim 1 , further comprising the step of releasing CSF toreduce the pressure in the subarachnoid space.
 6. The method of claim 1, further comprising the step of performing aortic surgery.
 7. Themethod of claim 6 , wherein the surgery is any one of thoracic andabdominal aortic aneurysm repair.
 8. The method of claim 1 , furthercomprising the step of mixing CSF with Ringer's lactate solution.
 9. Themethod of claim 1 , further comprising the step of adjusting the CSFflow rate.
 10. The method of claim 1 , further comprising the step ofmeasuring CSF temperature.
 11. The method of claim 1 , furthercomprising the step of infusing fluid or neuroprotective agent into thesubarachnoid space.
 12. A method for preventing neurologic damage,comprising the steps of: providing first and second elongate tubularmembers, each member having a lumen communicating with a port at adistal end; inserting the first tubular member between lumbar vertebraeinto the subarachnoid space; inserting the second tubular member betweenlow cervical vertebrae into the subarachnoid space, and advancing thedistal port cephalad or caudal and locating the port in the cervical,thoracic, or lumbar region of the spine; aspirating cerebral spinalfluid (CSF) from the spinal column through one of the first tubularmember or second tubular member; cooling the CSF by extracorporealrefrigeration; and perfusing the CSF into the spinal column through theother of the first tubular member or second tubular member, wherein thespinal cord is cooled to below normal body temperature and wherein CSFpressure is reduced to and maintained at a level substantially belownormal CSF pressure.
 13. The method of claim 12 , wherein the first andsecond tubular members are inserted over a needle.
 14. The method ofclaim 12 , further comprising the step of measuring CSF pressure using amanometer.
 15. The method of claim 12 , further comprising the step ofreleasing CSF to reduce the pressure in the subarachnoid space.
 16. Themethod of claim 12 , further comprising the step of performing aorticsurgery.
 17. The method of claim 16 , wherein the surgery is any one ofthoracic and abdominal aortic aneurysm repair.
 18. The method of claim12 , further comprising the step of infusing fluid into the subarachnoidspace, and wherein the CSF is mixed with the fluid.
 19. The method ofclaim 18 , wherein the fluid is Ringer's lactate or saline solution. 20.The method of claim 12 , further comprising the step of adjusting theCSF flow rate.
 21. The method of claim 12 , wherein the second tubularmember is inserted between vertebrae C6 and C7.
 22. The method of claim12 , wherein the second tubular member is inserted between vertebrae C7and T1.
 23. The method of claim 1 , wherein the method cools the spinalcord to prevent neurologic damage during inadequate spinal perfusion.